Personal activity monitors provide users with a convenient way of recording their physical activity. In particular, many so-called “fitness trackers” provide users with estimates of the distance they have walked or run, or the total energy they have expended and so forth. This kind of data allows users to make more informed decisions regarding their lifestyle. In some cases, a fitness tracker may remind the user to perform that they have not undertaken moderate or vigorous physical activity recently. While such fitness trackers may help individuals improve their health by motivating them to undertake more physical activity, other factors such as the food and drink the user consumes also play an important role in determining the wellbeing of the individual.
US2018/0374567A1 describes a wrist-worn barcode scanner for providing product recommendations to a user based on his or her personal biological information. The scanner includes sensors for measuring various physiological or biochemical functions of the user, such as his or her calorific expenditure or heart rate. The data obtained by the sensors is used to adjust the product recommendations. For example, if the data indicates that the user has not undertaken enough physical exercise then products with a high calorific content are no longer recommended.